1. Field of the Invention
The invention relates generally to a method of preparing water soluble polymer gels and, more particularly, the invention is directed to a process for preparing a water soluble polymer gel having a relatively narrow molecular weight distribution and a relatively high molecular weight.
2. Description of Background Technology
The production of water soluble polymers by the polymerization of water soluble vinyl monomers in aqueous solutions is well known. Such polymerizations are often carried out in solution using relatively dilute monomer (and resulting polymer) concentrations, and in gel polymerization systems wherein relatively concentrated monomer solutions and polymer gel products are obtained.
Gel polymerization processes are advantageously carried out in the substantial absence of oxygen (which is a polymerization inhibitor for vinyl monomers) in the presence of a suitable reaction initiator (e.g. organic free radical generating initiators, redox initiation systems, etc.) in deep reactors whereby a product having a thick cross-section is produced. The polymerization reaction is strongly exothermic and in a reactor wherein the depth of the product is large, temperature gradients tend to form which result in non-uniform reaction rates across the product, resulting in often widely variable molecular weight distributions in gel products.
Prior polymerization systems and equipment typically are large, complicated, and expensive, or require multiple steps for implementation and control, which may adversely affect quality control. In some cases, prior systems require multiple batch operation.
Prior thin film polymerization (i.e. continuous band polymerization) systems are mechanically and chemically complicated and very expensive.